1. Field of the Invention
This invention relates generally to exhaust systems. More particularly, the invention relates to an exhaust system for a multi-cylinder internal combustion engine.
2. Background
Motorcycles commonly employ exhaust systems to convey the exhaust gas from the engine""s cylinder to the ambient environment. The journey begins at the engine cylinder, which incorporates intake and exhaust ports for ingress and egress to the cylinder. Fresh air mixed with fuel enters the engine cylinder through the intake port where it is subsequently compressed by a piston and ignited. A rapid expansion of the compressed fuel and air occurs, thereby forcefully moving the piston in the opposite direction to the compression stroke. Once the expansion is complete, the exhaust port opens to allow the combustion by-products or gas to exit the engine cylinder and enter an exhaust pipe. The exhaust port may be a passageway into the engine cylinder that is uncovered by the retreating piston, as in a two-stroke design well known in the art. In the case of a four-stroke design, a valve is utilized to open or close the exhaust port. The exhaust gas expelled from the engine cylinder, after passing through the exhaust port, enters an exhaust pipe. The exhaust pipe is designed to direct the exhaust gas towards the rear of the motorcycle and commonly utilizes bends and curves to accomplish this goal.
In the case of a V-Twin Harley-Davidson(copyright) motorcycle engine, the design of the stock OEM exhaust system affects the motorcycle""s performance. The OEM exhaust system comprises a partial dual exhaust system with unequal length exhaust pipes from each cylinder. This system allows some communication between the exhaust gases from the cylinders via a crossover pipe. However, the design of this crossover pipe is detrimental to the engine""s performance. The exhaust gases from the cylinders interfere with each other as they are routed to two exhaust mufflers. Moreover, the routing path of the gases from the engine exhaust ports to the exhaust mufflers increases the exhaust systems backpressure.
The design of the stock OEM exhaust system for the V-Twin Harley-Davidson(copyright) motorcycle also affects the aural sensation experienced by the rider. For example, the sound of the OEM exhaust system is uneven as heard by the rider due to the exhaust system""s design. Further, during the engine""s transition from under load to a state of deceleration, the engine emits a staccato popping sound that is not pleasing to the ear. Any potential aftermarket fix for these performance and aural sensation issues is further complicated by the design of the Harley-Davidson(copyright) OEM exhaust system which attaches to the chassis of the motorcycle at fixed points, thus impeding any modifications to the exhaust system without permanent changes to the motorcycle.
One embodiment of the present invention is an exhaust system for a V-Twin motorcycle engine. This embodiments provides a substantial improvement to the well-known Harley-Davidson(copyright) engine.
One aspect of the aftermarket exhaust system constructed in accordance with one embodiment of the present invention is an exhaust system which comprises a first exhaust port in communication with a first cylinder of the engine to discharge a first pulse of exhaust gas, a second exhaust port in communication with a second cylinder of the engine to discharge a second pulse of exhaust gas, wherein the first and second exhaust ports are both located on a first side of the V-Twin engine. The system further comprises a first exhaust pipe having an inlet end and an outlet end, wherein the inlet end is connected to the first exhaust port for scavenging and routing the first pulse of exhaust gas along the first side and in a direction aft of the motorcycle chassis, a second exhaust pipe having an inlet end and an outlet end, wherein the inlet end is connected to the second exhaust port for scavenge and routing the second pulse of exhaust gas through the motorcycle chassis and along a second side of the V-Twin engine in a direction aft of the motorcycle chassis, wherein the first and second sides are substantially parallel with the motorcycle chassis, and wherein the second exhaust pipe utilizes an OEM attachment point to the motorcycle chassis. The system still further comprises a first muffler connected to and in flow communication with the first exhaust pipe, wherein the first pulse of exhaust gas is expelled through the first muffler to the atmosphere, and a second muffler connected to and in flow communication with the second exhaust pipe, wherein the second pulse of exhaust gas is expelled through the second muffler to the atmosphere.
Another aspect of the present invention is a motorcycle with a two cylinder V-Twin engine and a true dual exhaust system wherein the true dual exhaust system individually routes exhaust gases from the two cylinders to a pair of mufflers.
Still another aspect of the present invention is a motorcycle that comprises a frame, a V-twin engine attached to the frame and having a first and a second cylinder head, each containing a cylinder, wherein the first and second cylinder heads exhaust gas on a same side of the V-twin engine, and a dual exhaust system in flow communication with the two cylinder heads and configured to route exhaust gases from the two cylinders, to different sides of the frame, and to the atmosphere.
Yet another aspect of the present invention is an exhaust system component for a Harley-Davidson(copyright) motorcycle with a V-Twin engine, wherein the V-twin engine comprises first and second exhaust ports, both located on a first side of the V-twin engine, and wherein the second exhaust port is located rearward of the first exhaust port. The exhaust system component comprises an exhaust pipe having an inlet end and an outlet end, wherein the inlet end is configured to route exhaust gases from the second exhaust port and through the motorcycle and along a second side of the V-Twin engine in a direction rearward of the motorcycle, wherein the first and second sides are substantially parallel with the motorcycle, and wherein the exhaust pipe utilizes an OEM attachment point to the motorcycle.
Still another aspect of the present invention is a method of processing exhaust gases from a V-Twin engine in a motorcycle, wherein a first pulse of exhaust gas is produced in a first cylinder of the V-Twin engine and a second pulse of exhaust gas is produced in a second cylinder of the V-Twin engine. The method comprises routing the first pulse of exhaust gas from the first cylinder and along a first side of the V-Twin engine, wherein the first cylinder exhausts the first pulse of gas on the first side of the V-Twin engine, and routing the second pulse of exhaust gas from the second cylinder and along the first side of the V-Twin engine and back under a seat of the motorcycle to a second side of the V-Twin engine, wherein the second cylinder exhausts the second pulse of gas on the first side of the V-Twin engine, and wherein the first pulse of exhaust gas and the second pulse of exhaust gas follow different flow paths.